CN115073343A - Caprolactam synthesis method without by-product ammonium sulfate - Google Patents
Caprolactam synthesis method without by-product ammonium sulfate Download PDFInfo
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Abstract
The invention provides a caprolactam synthesis method without by-product ammonium sulfate, which comprises the steps of designing a special process route, selecting a specific solvent, taking cyclohexanone oxime as a raw material, and catalyzing Beckmann rearrangement reaction by fuming sulfuric acid to obtain a caprolactam product; the caprolactam-sulfuric acid phase is separated from the solvent phase after the Beckmann rearrangement reaction, and the reaction heat can be reduced in the reaction process; by optimizing the reaction process route, ammonia gas is not consumed, the consumption of sulfuric acid is disposable, and the consumption of sulfuric acid is basically zero when the reactor runs for a long time; finally, the method can realize no by-product ammonium sulfate, and has mild reaction conditions and high product yield.
Description
Technical Field
The invention belongs to the technical field of chemical synthesis, and particularly relates to a catalyst for preparing caprolactam through Beckmann rearrangement and a preparation method thereof.
Background
Caprolactam is an important organic chemical raw material, and is mainly used as a monomer of a high polymer due to a special structure, and polyamide 6(PA6) chips are produced through polymerization. The PA6 slices with different brands have different performances and different application fields, and the processed and molded PA6 is widely applied to the fields of textiles, packaging, automobiles, electronics, machinery and the like.
The world's caprolactam production raw material route is mainly benzene, phenol and toluene. The toluene path in the three raw materials has the highest capacity, and is the world's most important caprolactam production method. The technology of DSM company in the Netherlands is taken as a representative, cyclohexanone oxime is synthesized by preparing cyclohexanone, and caprolactam is obtained by Beckmann rearrangement. In recent years, the caprolactam production technology in China is greatly improved, and the domestic productivity is greatly expanded.
The Beckmann rearrangement (Beckmann rearrangement) is a rearrangement reaction catalyzed by an acid, and oxime as a reactant is rearranged into an amide under the catalysis of the acid. Various beckmann rearrangement catalysts are available, including inorganic acids, organic acids, acidic molecular sieves, ionic liquids, and the like.
In the industrial production of caprolactam, sulfuric acid or oleum is often used as a catalyst, and caprolactam is produced by the beckmann rearrangement reaction of cyclohexanone oxime in the presence of sulfuric acid or oleum. The process generally adopts a mode of material external circulation heat transfer, namely, fuming sulfuric acid is added into a system from a circulating pump inlet in a rearrangement reactor and mixed with rearrangement liquid, heat is transferred out of a reaction system through a circulating pipeline heat exchanger, and the circulation liquid with the reduced temperature enters a mixer and is rapidly mixed with added cyclohexanone oxime to react to form heavy liquid. The process is mature and simple, so that the caprolactam is basically produced by the method in industry.
The rearrangement reaction of cyclohexanone oxime in the presence of oleum is a strong exothermic reaction, the reaction speed is high, the reaction is violent, and a large amount of impurities are generated due to poor system configuration, so that the product quality of caprolactam is seriously influenced. More seriously, the process also produces a large amount of ammonium sulfate, and 1.4 to 1.8 tons of ammonium sulfate are produced per 1 ton of caprolactam. Ammonium sulfate is a chemical fertilizer, which is sold at a price lower than the cost price, and a large amount of ammonium sulfate by-products cause an increase in the cost. Therefore, the process needs to be improved, the consumption of sulfuric acid and ammonia gas is reduced, and the yield of the by-product ammonium sulfate is reduced, so that the production cost is reduced.
In patent US4257950, cyclohexanone oxime is subjected to beckmann rearrangement using nicotinic acid as a catalyst to produce caprolactam by dissolving in a solvent which is inert to nicotinic acid and insoluble in water and nicotinic acid, but ammonium sulfate by-produced is not reduced.
Patent CN1508128A also discloses a method for preparing caprolactam from cyclohexanone oxime and nicotinic acid or anhydrous sulfuric acid in the presence of a solvent inert to nicotinic acid or sulfuric acid, but with the by-product of ammonium sulfate.
Disclosure of Invention
The method uses cyclohexanone oxime as a raw material and obtains a caprolactam product by catalyzing Beckmann rearrangement reaction with fuming sulfuric acid. Compared with the prior art, the method has the advantages of no by-product of ammonium sulfate, mild reaction conditions, high yield and the like, and is suitable for industrial production.
Specifically, the caprolactam synthesis method without by-product ammonium sulfate comprises the following steps:
(1) slowly adding caprolactam into fuming sulfuric acid, and stirring until the caprolactam is fully dissolved to form caprolactam-sulfate;
(2) placing cyclohexanone oxime in a solvent, and stirring until the cyclohexanone oxime is dissolved;
(3) preheating the cyclohexanone oxime solution obtained in the step (2), preheating the caprolactam-sulfate obtained in the step (1), adding the cyclohexanone oxime solution into the caprolactam-sulfate to obtain a two-phase mixed solution, stirring until the two-phase mixed solution is uniformly mixed, and keeping the temperature for a period of time;
(3) separating the two phases obtained in step (2) to obtain a lighter solvent phase and a heavier caprolactam-sulfuric acid phase;
(4) rectifying and separating the solvent phase obtained in the step (3) to obtain a caprolactam product, wherein the solvent obtained by rectification can be repeatedly used; the rectification is reduced pressure rectification, the absolute pressure is 2-12 kPa, the preferable pressure is 4-8 kPa, and the temperature of the caprolactam fraction is 130-190 ℃, and the preferable temperature is 162-183 ℃.
(5) Collecting the caprolactam-sulfate obtained in the step (3), and removing a small amount of entrained solvent by flash evaporation purification, wherein the caprolactam-sulfate can be reused as a catalyst. The flash evaporation temperature of the caprolactam-sulfate is 50-120 ℃, the flash evaporation temperature is preferably 80-100 ℃, and the flash evaporation pressure is 2-36 kPa, and is preferably 10-20 kPa.
In the step (2), the selected solvent is one or more of carbon tetrachloride, chlorobenzene, dichlorobenzene, propyl ether, ethyl propyl ether, butyl ether, 1-chloropropane, ethylene glycol dimethyl ester and propyl propionate, and preferably one or more of carbon tetrachloride, chlorobenzene, dichlorobenzene, propyl ether, ethyl propyl ether and butyl ether.
In the step (1), the concentration of the fuming sulfuric acid is 3-40%, and the preferable concentration is 8-20%.
The mass ratio of the caprolactam to the oleum is 0.5-3, and the preferred mass ratio is 0.8-2.
The adding step is heating caprolactam to 80 ℃ to fully melt the caprolactam, gradually adding the caprolactam into fuming sulfuric acid, wherein the adding time is not less than 10min, quickly stirring the fuming sulfuric acid during adding, and cooling the fuming sulfuric acid to keep the temperature below 100 ℃. Continuing to stir the caprolactam-sulfuric acid mixture after the addition is completed until a uniform liquid is formed;
in the step (2), the mass concentration of the cyclohexanone oxime is 5-30 wt%, and the preferable concentration is 5-20 wt%.
In the step (3), the preheating temperature of the cyclohexanone oxime solution is 50-250 ℃, preferably 100-180 ℃, and the preheating temperature of the caprolactam-sulfate is 50-250 ℃, preferably 100-180 ℃. The mass ratio of the caprolactam-sulfate to the cyclohexanone oxime is 0.5-20, preferably 3-10, the reaction temperature is 50-170 ℃, preferably 100-130 ℃, and the reaction time is 0.5-30 min, preferably 5-15 min;
in the step (4), the rectification is reduced pressure rectification, the absolute pressure is 2-12 kPa, preferably 4-8 kPa, the fraction temperature of caprolactam is 130-190 ℃, and preferably 162-183 ℃;
in the step (5), the flash evaporation temperature of the caprolactam-sulfate is 50-120 ℃, preferably 80-100 ℃, and the flash evaporation pressure is 2-36 kPa, preferably 10-20 kPa.
Has the advantages that:
the invention provides a caprolactam synthetic method without by-product ammonium sulfate, which is characterized in that a special process route is designed, a specific solvent is selected, a caprolactam-sulfuric acid phase is separated from a solvent phase, and the reaction heat can be reduced in the reaction process; by optimizing the reaction process route, ammonia gas is not consumed, the consumption of sulfuric acid is disposable, and the consumption of sulfuric acid is basically zero when the reactor runs for a long time; finally, the method can realize no by-product ammonium sulfate, and has mild reaction conditions and high product yield.
Drawings
FIG. 1 is a process flow diagram of a caprolactam synthesis method without by-product ammonium sulfate.
Detailed Description
The present invention will be described in detail with reference to examples.
Example 1
8kg of caprolactam were heated to 80 ℃ and allowed to melt sufficiently. And slowly adding the melted caprolactam into 6kg of 10% fuming sulfuric acid, and stirring uniformly to obtain caprolactam-sulfate. 4kg of cyclohexanone oxime was dissolved in 27.5kg of carbon tetrachloride and stirred until sufficiently dissolved. Preheating the cyclohexanone oxime solution and caprolactam-sulfate to 140 ℃, respectively, adding the cyclohexanone oxime solution into the caprolactam-sulfate to obtain a two-phase mixed solution, quickly stirring until the two-phase mixed solution is uniformly mixed, keeping the temperature at 140 ℃, keeping the temperature, and reacting for 15 min. After the reaction is finished, the stirring is stopped, and the two phases are separated to obtain a solvent phase and a caprolactam-sulfate phase. And rectifying the obtained solvent phase at the absolute pressure of 4kPa and the caprolactam fraction temperature of 170 ℃ to obtain a caprolactam product.
Analysis shows that the conversion rate of the cyclohexanone-oxime is 100 percent, the selectivity of the caprolactam is 98.2 percent, the yield of the rectified caprolactam is 3.86kg, and the yield is 96.5 percent.
Example 2
14kg of caprolactam were heated to 80 ℃ and allowed to melt well. Slowly adding the melted caprolactam into 10kg of 18% fuming sulfuric acid, and stirring the mixture until the mixture is uniform to obtain caprolactam-sulfate. 6kg of cyclohexanone oxime was dissolved in 50kg of dichlorobenzene, and stirred until sufficiently dissolved. Preheating the cyclohexanone oxime solution and caprolactam-sulfate to 170 ℃ respectively, adding the cyclohexanone oxime solution into the caprolactam-sulfate to obtain a two-phase mixed solution, quickly stirring until the two-phase mixed solution is uniformly mixed, keeping the temperature at 170 ℃, keeping the temperature, and keeping the reaction time at 8 min. After the reaction is finished, the stirring is stopped, and the two phases are separated to obtain a solvent phase and a caprolactam-sulfate phase. And rectifying the obtained solvent phase at 7kPa and 183 ℃ to obtain a caprolactam product. Through analysis, the conversion rate of the cyclohexanone-oxime is 100%, the selectivity of the caprolactam is 99.3%, the yield of the rectified caprolactam is 5.87kg, and the yield is 97.8%.
Example 3
18kg of caprolactam were heated to 80 ℃ and allowed to melt well. Slowly adding the melted caprolactam into 10kg of oleum with the concentration of 15%, and stirring the mixture until the mixture is uniform to obtain caprolactam-sulfate. 2.9kg of cyclohexanone oxime was dissolved in 25kg of chlorobenzene and stirred until sufficiently dissolved. Preheating the cyclohexanone oxime solution and caprolactam-sulfate to 170 ℃ respectively, adding the cyclohexanone oxime solution into the caprolactam-sulfate to obtain a two-phase mixed solution, quickly stirring until the two-phase mixed solution is uniformly mixed, keeping the temperature at 170 ℃, keeping the temperature, and reacting for 10 min. And after the reaction is finished, stopping stirring, separating phases of the two phases, rectifying the solvent phase and the solvent phase obtained from the caprolactam-sulfate phase, wherein the rectification pressure is 6kPa, and the distillation temperature of caprolactam is 175 ℃ to obtain a caprolactam product.
Through analysis, the conversion rate of the cyclohexanone-oxime is 100%, the selectivity of the caprolactam is 98.3%, the yield of the rectified caprolactam is 2.82kg, and the yield is 97.2%.
Example 4
20kg of caprolactam were heated to 80 ℃ and allowed to melt well. Slowly adding the melted caprolactam into 10kg of fuming sulfuric acid with the concentration of 20 percent, and stirring the mixture until the mixture is uniform to obtain caprolactam-sulfate. 10kg of cyclohexanone oxime was dissolved in 180kg of propyl ether, and stirred until sufficiently dissolved. Preheating the cyclohexanone oxime solution and caprolactam-sulfate to 150 ℃ respectively, adding the cyclohexanone oxime solution into the caprolactam-sulfate to obtain a two-phase mixed solution, quickly stirring until the two-phase mixed solution is uniformly mixed, keeping the temperature at 150 ℃, keeping the temperature, and keeping the reaction time at 15 min. After the reaction is finished, the stirring is stopped, and the two phases are separated to obtain a solvent phase and a caprolactam-sulfate phase. And rectifying the obtained solvent phase at absolute pressure of 6kPa and caprolactam fraction temperature of 162 ℃ to obtain a caprolactam product.
Through analysis, the conversion rate of the cyclohexanone-oxime is 99.9 percent, the selectivity of the caprolactam is 97.8 percent, the yield of the rectified caprolactam is 9.55kg, and the yield is 95.5 percent.
Example 5
8kg of caprolactam were heated to 80 ℃ and allowed to melt sufficiently. Slowly adding the melted caprolactam into 10kg of oleum with the concentration of 15%, and stirring the mixture until the mixture is uniform to obtain caprolactam-sulfate. 4kg of cyclohexanone oxime was dissolved in 32kg of butyl ether and stirred until sufficiently dissolved. Preheating the cyclohexanone oxime solution and caprolactam-sulfate to 130 ℃, respectively, adding the cyclohexanone oxime solution into the caprolactam-sulfate to obtain a two-phase mixed solution, quickly stirring until the two-phase mixed solution is uniformly mixed, keeping the temperature at 130 ℃, keeping the temperature, and reacting for 15 min. After the reaction is finished, the stirring is stopped, and the two phases are separated to obtain a solvent phase and a caprolactam-sulfate phase. And rectifying the obtained solvent phase at the absolute pressure of 8kPa and the caprolactam fraction temperature of 170 ℃ to obtain a caprolactam product.
Through analysis, the conversion rate of the cyclohexanone-oxime is 100%, the selectivity of the caprolactam is 94.8%, the yield of the rectified caprolactam is 3.56kg, and the yield is 89.3%.
Example 6
10kg of caprolactam were heated to 80 ℃ and allowed to melt well. Slowly adding the melted caprolactam into 10kg of 10% fuming sulfuric acid, and stirring the mixture until the mixture is uniform to obtain caprolactam-sulfate. 5kg of cyclohexanone oxime was dissolved in 90kg of ethyl ether, and stirred until sufficiently dissolved. Preheating the cyclohexanone oxime solution and caprolactam-sulfate to 100 ℃, respectively, adding the cyclohexanone oxime solution into the caprolactam-sulfate to obtain a two-phase mixed solution, quickly stirring until the two-phase mixed solution is uniformly mixed, keeping the temperature at 100 ℃, keeping the temperature, and reacting for 12 min. After the reaction is finished, the stirring is stopped, and the two phases are separated to obtain a solvent phase and a caprolactam-sulfate phase. And rectifying the obtained solvent phase at 7kPa and 168 ℃ to obtain a caprolactam product.
Through analysis, the conversion rate of the cyclohexanone-oxime is 100%, the selectivity of the caprolactam is 98.9%, the yield of the rectified caprolactam is 4.91kg, and the yield is 98.2%.
Comparative example 1
10kg of cyclohexanone oxime was preheated to 100 ℃ and 10kg of 10% oleum was taken and preheated to 100 ℃. Slowly spraying and adding the cyclohexanone oxime solution into fuming sulfuric acid, continuously stirring, keeping the reaction temperature at 100 ℃, and stopping the reaction after 5min of reaction to obtain a caprolactam-sulfuric acid phase. The caprolactam-sulfuric acid phase was placed in 20kg of saturated aqueous ammonium sulfate solution, the temperature was kept at 45 ℃, stirring was started and ammonia gas was gradually introduced into it, the liquid separated into three phases after introduction, and the pH of the lower aqueous phase was 6.0. Taking 16kg of caprolactam phase as the upper layer, placing the caprolactam phase in 15kg of benzene, keeping the temperature at 45 ℃, and stirring until the extraction is finished. Taking 27.1kg of caprolactam-benzene phase on the upper layer, placing the caprolactam-benzene phase in 10kg of water, keeping the temperature at 30 ℃, and stirring until the extraction is finished to obtain a caprolactam water solution.
Through analysis, the conversion rate of the cyclohexanone oxime is 100 percent, the selectivity of the caprolactam is 98.7 percent, the yield of the caprolactam after neutralization crystallization-extraction treatment is 38.7kg, the yield is 96.8 percent, the amount of the ammonium sulfate byproduct is 55.1kg, and 1.42kg of the ammonium sulfate byproduct is produced per kg of the caprolactam.
Comparative example 2
12kg of caprolactam were heated to 80 ℃ and allowed to melt well. Slowly adding the melted caprolactam into 10kg of 10% fuming sulfuric acid, and stirring the mixture until the mixture is uniform to obtain caprolactam-sulfate. 3kg of cyclohexanone oxime was dissolved in 25kg of t-butanol, and stirred until sufficiently dissolved. Preheating the cyclohexanone oxime solution and caprolactam-sulfate to 80 ℃, respectively, adding the cyclohexanone oxime solution into the caprolactam-sulfate to obtain a two-phase mixed solution, quickly stirring until the two-phase mixed solution is uniformly mixed, keeping the temperature at 80 ℃, keeping the temperature, and reacting for 5 min. After the reaction is finished, the stirring is stopped, the reaction product is a single phase, and the caprolactam-sulfate are both dissolved in the solvent. A caprolactam solution containing no sulfuric acid could not be obtained, and caprolactam could not be obtained without by-producing ammonium sulfate.
The cyclohexanone oxime conversion was 98.5% and caprolactam selectivity was 93.9% as analyzed.
Comparative example 3
8kg of caprolactam were heated to 80 ℃ and allowed to melt sufficiently. And slowly adding the melted caprolactam into 6kg of 10% fuming sulfuric acid, and stirring uniformly to obtain caprolactam-sulfate. 4kg of cyclohexanone oxime was dissolved in 27.5kg of cyclooctane and stirred until sufficiently dissolved. Preheating the cyclohexanone oxime solution and caprolactam-sulfate to 140 ℃, respectively, adding the cyclohexanone oxime solution into the caprolactam-sulfate to obtain a two-phase mixed solution, quickly stirring until the two-phase mixed solution is uniformly mixed, keeping the temperature at 140 ℃, keeping the temperature, and reacting for 15 min. After the reaction is finished, the stirring is stopped, and the two phases are separated to obtain a solvent phase and a caprolactam-sulfate phase. Rectifying the obtained solvent phase to obtain a caprolactam product.
Through analysis, the conversion rate of the cyclohexanone-oxime is 100 percent, the selectivity of the caprolactam is 94.2 percent, the yield of the rectified caprolactam is 0.058kg, and the yield is 1.45 percent.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (10)
1. A caprolactam synthesis method without by-product ammonium sulfate is characterized by comprising the following steps:
(1) slowly adding caprolactam into fuming sulfuric acid, and stirring until the caprolactam is fully dissolved to form caprolactam-sulfate;
(2) placing cyclohexanone oxime in a solvent, and stirring until the cyclohexanone oxime is dissolved to form a cyclohexanone oxime solution;
(3) preheating the cyclohexanone oxime solution obtained in the step (2), preheating the caprolactam-sulfate solution obtained in the step (1), adding the cyclohexanone oxime solution into caprolactam-sulfate to obtain a two-phase mixed solution, stirring until the two-phase mixed solution is uniformly mixed, and keeping the temperature;
(3) separating the two phases obtained in step (2) to obtain a lighter solvent phase and a heavier caprolactam-sulfuric acid phase;
(4) rectifying and separating the solvent phase obtained in the step (3) to obtain a caprolactam product, wherein the solvent obtained by rectification can be repeatedly used;
(5) collecting the caprolactam-sulfate obtained in the step (3), and purifying by flash evaporation, wherein the caprolactam-sulfate can be used as a catalyst repeatedly.
2. The process for synthesis of caprolactam of claim 1, wherein: the solvent in the step (2) is one or more of carbon tetrachloride, chlorobenzene, dichlorobenzene, propyl ether, ethyl propyl ether, butyl ether, 1-chloropropane, ethylene glycol dimethyl ester and propyl propionate, and preferably one or more of carbon tetrachloride, chlorobenzene, dichlorobenzene, propyl ether, ethyl propyl ether and butyl ether.
3. The process for synthesis of caprolactam of claim 1, wherein: in the step (1), the concentration of the fuming sulfuric acid is 3-40%, and the preferable concentration is 8-20%.
4. A process for the synthesis of caprolactam according to claim 1, characterized in that: in the step (1), the mass ratio of caprolactam to oleum is 0.5-3, and the preferable mass ratio is 0.8-2.
5. The process for synthesis of caprolactam of claim 1, wherein: in the step (1), the adding step is heating caprolactam to 80 ℃ to fully melt the caprolactam, gradually adding the caprolactam into fuming sulfuric acid, wherein the adding time is not less than 10min, quickly stirring the fuming sulfuric acid during adding, cooling the fuming sulfuric acid to keep the temperature below 100 ℃, and continuously stirring the caprolactam-sulfuric acid mixture until a uniform liquid is formed after adding.
6. The process for synthesis of caprolactam of claim 1, wherein: in the step (2), the mass concentration of the cyclohexanone oxime is 5-30 wt%, and the preferable concentration is 5-20 wt%.
7. The process for synthesis of caprolactam of claim 1, wherein: in the step (3), the preheating temperature of the cyclohexanone oxime solution is 50-250 ℃, preferably 100-180 ℃, and the preheating temperature of the caprolactam-sulfate is 50-250 ℃, preferably 100-180 ℃.
8. The process for synthesis of caprolactam of claim 1, wherein: in the step (3), the mass ratio of the caprolactam-sulfate to the cyclohexanone oxime is 0.5-20, preferably 3-10, the reaction temperature is 50-250 ℃, preferably 100-180 ℃, and the reaction time is 0.5-30 min, preferably 5-15 min.
9. A process for the synthesis of caprolactam according to claim 1, characterized in that: in the step (4), the rectification is reduced pressure rectification, the absolute pressure is 2-12 kPa, preferably 4-8 kPa, and the fraction temperature of caprolactam is 130-190 ℃, preferably 162-183 ℃.
10. The process for synthesis of caprolactam of claim 1, wherein: in the step (5), the flash evaporation temperature of the caprolactam-sulfate is 50-120 ℃, preferably 80-100 ℃, and the flash evaporation pressure is 2-36 kPa, preferably 10-20 kPa.
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| CN107311929B (en) * | 2016-04-27 | 2021-06-04 | 中国石油化工股份有限公司 | Preparation method of caprolactam |
| CN110683989A (en) * | 2019-10-14 | 2020-01-14 | 清华大学 | Heterogeneous rearrangement method for preparing caprolactam from cyclohexanone oxime |
| CN115073343B (en) * | 2022-06-29 | 2023-09-29 | 中国天辰工程有限公司 | Caprolactam synthesis method without by-product ammonium sulfate |
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|---|---|---|---|---|
| GB841383A (en) * | 1956-11-10 | 1960-07-13 | Bayer Ag | Process for the production of pure ª-caprolactam from beckmann reaction mixture |
| US3470153A (en) * | 1965-11-03 | 1969-09-30 | Inventa Ag | Process for the simultaneous production of epsilon-caprolactam and omega-dodecalactam |
| US3544562A (en) * | 1966-06-30 | 1970-12-01 | Inventa Ag | Process for the manufacture of omega-decalactam using epsilon-caprolactam as a solvent therefor |
| US4017482A (en) * | 1974-09-11 | 1977-04-12 | Basf Aktiengesellschaft | Method of purifying caprolactam |
| US4257950A (en) * | 1978-10-16 | 1981-03-24 | Basf Aktiengesellschaft | Continuous preparation of ε-caprolactam by Beckmann rearrangement |
| US20070055061A1 (en) * | 2003-05-23 | 2007-03-08 | Lemmens Joannes Albertus Wilhe | Continuous process for preparing caprolactam |
| US20140171638A1 (en) * | 2012-12-19 | 2014-06-19 | Basf Se | Process for preparing purified caprolactam from the beckmann rearrangement of cyclohexane oxime |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2024000848A1 (en) * | 2022-06-29 | 2024-01-04 | 中国天辰工程有限公司 | Caprolactam synthesis method free of by-production of ammonium sulfate |
Also Published As
| Publication number | Publication date |
|---|---|
| WO2024000848A1 (en) | 2024-01-04 |
| CN115073343B (en) | 2023-09-29 |
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